Are Epileptic K-Complexes and Small Sharp Spikes During Sleep Clinically Useful in the Evaluation of Epileptic Patients? Important Phenomenology Needs Consideration

IntroductionEpileptiform K complexes (eKC) and small sharp spikes (SSS) have been explored in a limited number of studies, with their relationhip to epileptic disorders remaining controversial. This retrospective study aimed to evaluate the significance of eKC and SSS in patients with epilepsy for clinical practice.MethodsAmong 370 consecutive patients over the age of 18, who underwent long-term video EEG monitoring, 63 were included based on having at least 20 min of recording after sleep onset and sufficient clinical data. eKC and SSS were visually analyzed by two investigators. Statistical comparisons were made between demographic and clinical data, EEG and neuroimaging features, prognostic evaluations of patients with and without eKC and SSS.ResultsAmong the 63 patients investigated, 38.1% exhibited eKC, and 14.3% showed SSS in their sleep recordings, with all affected individuals diagnosed with focal epilepsy syndromes. Compared to patients without eKCs, those with eKCs showed more frequent interictal bilateral slow waves during wakefulness (<i>p</i> = .045), and their ictal EEGs were less lateralized (<i>p</i> = .041). We found that eKCs were more likely to be detected with longer sleep analysis durations (<i>p</i> = .004). In the presence of SSS, ictal EEG was significantly more lateralized (<i>p</i> = .017) and associated with favorable surgical outcomes in patients who underwent epilepsy surgery (<i>p</i> = .015).ConclusionOur analysis highlight that eKC and SSS can be present in focal epilepsy syndromes. When considered as an epileptiform EEG phenomenon in drug-resistant epilepsy, these EEG findings may provide additional information during presurgical evaluation and SSS may help to predict surgical outcome.